EP1507488B1 - Arrangement for determining function-determined geometric variables of a joint of a vertebrate - Google Patents

Abstract

Arrangement for ascertaining function-determining geometric parameters of a joint of a vertebrate, especially a hip or shoulder joint of a human being, in preparation for the installation of a joint replacement implant, especially a hip or shoulder socket or an associated stem implant, by means of an optical coordinate-measuring procedure, having a stereocamera or stereocamera arrangement for the spatial recording of optical transducer signals, a mobile multipoint transducer which is in the form of a movable sensor for sensing bony references in the joint region in order to determine the coordinates thereof, at least one bone-fixed multipoint transducer which is configured for rigid attachment, especially screwed or clamped attachment, (in a region sufficiently distant from the joint) to an extremity originating from the joint, especially close to the proximal end of a femur or a humerus, an interactive sequence controller for controlling the sequential registration and storage of a set of measurement point coordinates supplied by the mobile multipoint transducer and sets of measurement point coordinates recorded in a first plurality of positions of the bone-fixed multipoint transducer in a plurality of rotated positions of the extremity and their subsequent processing in accordance with a previously stored processing sequence, an evaluation unit for evaluating the sets of measurement point coordinates supplied by the multipoint transducers and recorded by the camera arrangement for the purpose of determining the geometric parameters, which comprises means for determining the transversal, vertical and sagittal body axes as well as means for carrying out an iterative procedure, especially an adjustment calculation in accordance with the least squares method, to determine the coordinates of the center of rotation of the joint, and an output unit, which is connected to the sequence controller and to the evaluation unit, for issuing manipulation proposals to an operating surgeon in accordance with the predetermined process sequence and in dependence upon the results of the determination of the geometric parameters, and for displaying the results of the evaluation.

Description

The invention relates to an arrangement for determining function-determining geometric variables of a joint of a vertebrate.

Surgical interventions for the replacement of joints or joint components in humans have been known for a long time and are part of everyday clinical practice in industrialized countries. There has also been intensive development work for decades to provide and continuously improve corresponding implants, in particular hip joint implants, but increasingly also knee, shoulder and elbow joint implants, as well as vertebral body replacement implants. In parallel to these developments, which have now led to an almost incalculable variety of such implant designs, also suitable surgical techniques and tools are provided and further developed, in particular adapted to the respective implant designs tools for inserting the same.

It is also understood that joint replacement surgery precedes the acquisition of appropriate images of the respective joint area, based on which the surgeon determines a suitable implant and its surgical technique. In the past, X-rays were mostly used for this purpose, but in recent years computer tomograms have become the tool of the surgeon. Nevertheless, the long-term success of joint replacement implants is still closely correlated with surgeon experience, due in large part to the not inconsiderable difficulties of adequate intraoperative use of visual images for optimal alignment of the parts of the joint implant with respect to the effective joint centers and joints Stress axes of the individual patient is due.

There has therefore been an increasing effort in recent years to provide appropriate positioning aids and procedures for the surgeon, which are essentially derived from developments in the field of robotics and handling technology.

The EP 0 553 266 B1 or US 5,198,877 describe a non-contact three-dimensional shape detection method and apparatus that has provided ideas for developing medical "navigation" systems and methods; see. also the detailed bibliography in these publications.

From the US 5,871,018 and the US 5,682,886 Methods are known for determining the load axis of the femur. According to these methods, in a first step, the coordinates of the femur are determined, for example, by a computed tomography image and stored in a computer. With the aid of the stored data, a three-dimensional computer model of the femur is then created, and this model is used to calculate the optimal coordinates for attaching a graft to the bone and a subsequently used knee prosthesis. The basis for this is the calculation of the load axis of the femur.

After such a simulation, the femur of the patient is fixed, and with a registration device, individual points on the femur surface are scanned to determine the orientation of the femur for the operation to be performed. This palpation of the bone requires that either large portions along the femur must be exposed as far as possible to the hip joint in order to be able to scan the surface thereof with the registration device, or a type of needle for puncturing the skin down to the bone is used as a scanning instrument. However, because any surgical procedure presents a risk to the patient and needle pricks cause bruising and an additional risk of infection in the bony areas, it is not desirable to perform additional hip surgery or make needle punctures along the femur to determine the location of the center of rotation , Furthermore, a strict fixation of the femur on a measuring table of the registration device is necessary, since otherwise shifts of the acetabular cup occur during the probing procedure and the cutting gauge would be incorrectly set after registration of the femoral coordinates.

The FR 2 785 517 describes a method and apparatus for detecting the center of rotation of the femoral head in the acetabulum. For this purpose, the femur is moved with its femoral head in the acetabular cup, and the measuring point coordinates recorded in different positions of the femur are stored. As soon as there is a shift in the center of rotation of the femur, a corresponding counterpressure is exerted on the femoral head, which is taken into account in the determination of a point which is related to the arrangement of the femur.

In the DE 197 09 960 A1 describe a method and a device for the preoperative determination of the position data of endoprosthesis parts of a middle joint relative to the bone forming the middle joint. In this case, it is proposed that in each case an outer point of articulation is determined by movement of the bones about an outer joint which is located at the end of the respective bone facing away from the middle joint, that in the region of the said central joint for each of the two bones also determines a point of articulation that determines a straightforward connection of the two joint points so found for each of the two bones a characteristic for this direction and finally determines the orientation of Endoprothesenteile relative to this characteristic direction.

Similar medical "navigation" procedures are used in the WO 95/00075 and the WO 99/23956 in which image acquisition systems of the type mentioned above are used for position detection of references to the bone adjacent to the respective joint, and characteristic points or axes can be derived from the virtual representation of the bone or joint obtained with their help.

An improved in terms of reliability and in particular the independence of intraoperative movements of the patient and for immediate use during the operation, in particular the implantation of an artificial knee joint, provided system of this kind is the subject of the Applicant WO 02/17798 A1 ,

• einer Stereokamera oder -kameraanordnung zur räumlichen Erfassung optischer Gebersignale, - einem mobilen Mehrpunktgeber, der als beweglicher Taster zum Antasten knöcherner Referenzen im Gelenkbereich zur Bestimmung von deren Koordinaten ausgebildet ist,
• einem skelettfesten Mehrpunktgeber, der zur starren Befestigung, insbesondere zum Anschrauben oder Anklemmen, an einer vom dem Gelenk ausgehenden Extremität, insbesondere nahe dem proximalen Ende eines Femurs oder eines Humerus, ausgebildet ist,
• einer Ablaufsteuerung zur Steuerung der sequentiellen Registrierung und Abspeicherung von einer durch den mobilen Mehrpunktgeber gelieferten Messpunktkoordinatenmengen und von in einer ersten Mehrzahl von Positionen des skelettfesten Mehrpunktgebers in einer Mehrzahl von Drehstellungen der Extremität erfassten Messpunktkoordinatenmengen und deren anschließenden Verarbeitung nach einem vorgespeicherten Verarbeitungsablauf,
• einer Auswertungseinheit zur Auswertung der durch die Mehrpunktgeber gelieferten und die Kameraanordnung erfassten Messpunktkoordinatenmengen zwecks Bestimmung der Belastungsachse mittels einer Ausgleichungsrechnung nach der Methode der kleinsten Quadrate, und
• einer mit der Ablaufsteuerung sowie der Auswertungseinheit verbundenen Ausgabeeinheit zur Ausgabe von Handlungsaufforderungen an einen Operateur gemäß dem vorbestimmten Verfahrensablauf sowie zur Anzeige der Auswertungsergebnisse.

This document teaches an arrangement for determining the load axis of a limb of a person, in preparation for the insertion of a joint replacement implant, in particular a hip or shoulder joint socket or an associated shaft implant, by means of an optical coordinate measuring method

• a stereo camera or camera arrangement for the spatial detection of optical transmitter signals, - a mobile multipoint transmitter, which is designed as a movable probe for detecting bony references in the joint region for determining their coordinates,
• a skeletal multipoint transmitter designed for rigid attachment, in particular for screwing or clamping, on a limb extending from the joint, in particular near the proximal end of a femur or a humerus,
• a sequence controller for controlling the sequential registration and storage of measurement point coordinate quantities provided by the mobile multipoint transmitter and measurement point coordinate quantities acquired in a plurality of rotational positions of the extremity in a first plurality of positions of the skeletal multipoint transmitter and their subsequent processing after a prestored processing operation;
• an evaluation unit for evaluating the measurement point coordinate quantities supplied by the multipoint transmitters and detected by the camera arrangement for the purpose of determining the load axis by means of a least squares adjustment calculation, and
• an output unit connected to the sequence control and the evaluation unit for outputting action requests to an operator according to the predetermined method sequence and for displaying the evaluation results.

Based on the state of the art, the invention is based on the object of providing a device of this type which can be operated quickly and easily and with a very low risk of error for the surgeon, which makes it possible to achieve significantly improved surgical results especially for hip and shoulder joint implants.

This object is achieved by an arrangement having the features of claim 1. Advantageous embodiments of the inventive concept are the subject of the dependent claims. Whose objects are - in any combination with each other - even in modified embodiments within the scope of the present invention.

It is an essential concept of the invention to carry out the proposed arrangement for determining function-determining geometric sizes of a joint in preparation for a joint replacement implantation with a stereo camera or camera arrangement and two different types of signal generators for these. It is (at least) a first ("mobile") multi-point transmitter, which is designed as a movable probe for detecting bony references in the hinge region for determining their coordinates, and a second ("skeleton-fixed") multi-point transmitter, which is used for rigid attachment, in particular for screwing or clamping, in a sufficiently disregarded by the joint portion of an outgoing from the joint extremity, in particular near the proximal or distal end of a femur or a humerus, is formed.

Furthermore, the invention includes the idea of providing an interactive sequence control for controlling the sequential registration and storage of measurement point coordinate quantities acquired in a first plurality of probe positions of the first multi-point encoder and a second plurality of rotational positions of the extremity and their subsequent processing according to a predetermined processing sequence.

Finally, the invention includes the idea of providing a suitably designed evaluation unit for evaluating the measurement point coordinate quantity delivered by the multipoint transmitters and detecting the camera arrangement in order to determine the geometric parameters. This evaluation unit comprises the means for determining the transverse, vertical and sagittal body planes and axes and means for performing an iterative method, in particular a least squares adjustment calculation, for determining the coordinates of the center of rotation of the joint.

Finally, the inventive arrangement includes an output unit connected to the sequence control and the evaluation unit for outputting action requests to an operator according to the predetermined method sequence and in dependence on the results of the determination of the geometric variables and for displaying the evaluation results.

Conveniently, the mentioned output unit for displaying the evaluation results in graphical representation, in particular in a synoptic pictorial representation with an obtained by an imaging examination method two- or three-dimensional image of the joint area formed. The surgeon is thus - regardless of an advantageously implemented in the system interactive user interface and automatic control functions - a good way to gain a visual impression of the geometric conditions in the joint area and optionally the location of a tool or the implant relative to this given.

Especially for a pan implantation (in the hip and shoulder area), another skeletal multi-point encoder is used, which is firmly attached to a bony area on the socket side of the joint (approximately on the iliac crest) and its position signals in conjunction with those of the mobile probe to the cup-side Position determination serve.

Essential for a broad practical application of the proposed arrangement is an input interface connected to the sequence control and the evaluation unit for inputting positional relationship vectors between defined real or virtual points of the joint region and / or positional relationship vectors between such points within the joint region or from these to joint function relevant points on the Extremity outside of the joint area and / or implant parameters of a predetermined amount of insertable joint replacement implants or to specify possible implant positions and orientations. This is either a user interface for keyboard or voice input of data by the surgeon or an interface for transferring data from an evaluation program based on an imaging examination method or an interface combining these functions.

Conveniently, the arrangement includes at least one adjustable clamping device as an adapter for fixing the skeletal multi-point encoder on the extremity or the multi-point encoder on the extremity and joint, or an adequate fastening device based on anchored in bone screws or nails.

Furthermore, the mobile multipoint transmitter is designed for externally touching bony references on the second limb emanating from the joint to be replaced and optionally the second hip or shoulder joint, or another multipoint transmitter designed as a movable probe for probing such references is provided for this purpose. Then the evaluation unit is to evaluate the measuring point coordinates of these bony references for determination at least one of the geometric sizes, in particular the length of the limb formed.

It is also useful to supplement the arrangement by a third (skeleton-fixed) Mehrpunktgeber for substantially rigid attachment, in particular by means of an adjustable cuff, on a second extremity, which emanates from a non-operating second hip or shoulder joint. In this case, the evaluation unit then makes it possible to determine the geometric sizes of the second hip or shoulder joint as a reference for the geometric sizes of the first joint.

An integrated overall arrangement of the type according to the invention preferably also comprises a resection instrument, in particular a milling cutter or a rasp, for shaping the implantation region and / or a navigable setting instrument, in particular a screwing tool, for mounting the joint replacement implant. In association with one of these or both tools another Mehrpunktgeber is provided or it is the o.a. mobile multipoint encoder hereby used. This is rigidly connected to the respective tool to a geometrically calibrated, navigable tool-encoder unit, such that from the encoder signals of this unit position coordinates of an active portion of the instrument, and therefrom optionally position coordinates of a resection provided with the resection or the implant can be determined , In this case, the input interface is designed specifically for the input of instrument parameters of the resection instrument and / or tool parameters of the setting instrument.

In a further expedient development of the inventive concept, the arrangement comprises a probe, in particular medullary canal, for probing a medullary canal of the extremity originating from the joint, which can be connected to a multipoint emitter rigidly connected to a geometrically calibrated, navigable probe-donor unit such that The encoder signals of this unit, a direction vector of the medullary canal can be determined. It is understood that here the input interface must be suitable for the input of probe parameters.

The multivibrator (s) is / are preferably designed as a passive four-point transmitter with four Kungel reflector sections. In this case, the stereo camera or camera arrangement is assigned an illumination device with which the one or more multipoint emitters are illuminated, so that defined reflections are available for "mapping" the respective multi-point emitter. In order to avoid light reflections that disturb the surgeon, the illumination device preferably operates in the infrared range.

An embodiment of the proposed arrangement which largely supports the surgeon comprises a control signal generation unit connected to the evaluation unit and the matching processing unit. This is the implant position data or orientation data which is entered for comparison of a set of data entered via the input interface and adapted to the real position coordinates of the joint or vertebral region with currently detected real position coordinates of the active section of the resection or setting instrument and for determining a deviation between desired and actual values Position coordinates and output of deviation data or derived from the deviation control command, in particular by text or voice output and / or in a synoptic representation with the image trained.

Fig. 1

einen Beckenkamm-Lokator mit zugehöriger Klammer (Adapter), aufgeklemmt auf einen Beckenkamm, in perspektivischer Darstellung,

Fig. 2

zusätzlich einen Handtaster zum Antasten der Tischoberfläche zwecks Bestimmung der Tischebene sowie knöchener Referenzen am Beckenkamm (über der Haut), in perspektivischer Darstellung,

Fig. 3

zusätzlich zum Beckenkamm-Lokator eine perspektivische Darstellung eines Femur-Lokators mit zugehöriger Klammer zur Fixierung im proximalen Bereich eines Femurs,

Fig. 4

eine Kugeladapter-Handtaster-Kombination zur Bestimmung des Zentrums des Acetabulums in perspektivischer Darstellung,

Fig. 5

eine perspektivische Darstellung einer Fräser-Lokator-Kombination zum Fräsen des Sitzes für eine Hüftpfanne,

Fig. 6

eine schematische Ausschnittdarstellung eines Schirmbildes eines PC-Monitors zur visuellen Darstellung der Aussichten des Fräsers bezüglich des Beckens,

Fig. 7

eine perspektivische Darstellung einer Setzinstrument-Lokator-Kombination zum Eindrehen einer künstlichen Hüftpfanne in den vorbereiteten Sitz und

Fig. 8

eine perspektivische Darstellung einer Markkanalahlen-Lokator-Kombination zur Bestimmung des Verlaufes des Markkanals in einem Femur.

Incidentally, advantages and expediencies result from the following description of a preferred exemplary embodiment - an arrangement in conjunction with a method for implanting an artificial hip joint - in conjunction with the figures. From these show:

Fig. 1

a iliac crest locator with associated bracket (adapter), clamped on a iliac crest, in a perspective view,

Fig. 2

In addition, a hand-held button for touching the table surface for the purpose of determining the level of the table as well as bony references on the iliac crest (above the skin), in perspective view,

Fig. 3

in addition to the iliac crest locator, a perspective view of a femur locator with associated clamp for fixation in the proximal region of a femur,

Fig. 4

a ball adapter-hand button combination for determining the center of the acetabulum in perspective view,

Fig. 5

a perspective view of a cutter-locator combination for milling the seat for a hip socket,

Fig. 6

a schematic detail view of a screen of a PC monitor for visual representation of the prospects of the router with respect to the pelvis,

Fig. 7

a perspective view of a setting instrument Lokator combination for screwing an artificial acetabulum in the prepared seat and

Fig. 8

a perspective view of a Markkanalahlen-Lokator combination for determining the course of the medullary canal in a femur.

The following presentation is given primarily on the basis of a procedure for determining the relevant geometric variables and for implantation of a hip socket, but also on the - relatively independent - determination of the relevant geometric variables and the execution of the implantation of a shaft part as a second component of an artificial hip joint pointed.

1. 1. Größe der künstlichen Pfanne
2. 2. Inklinationswinkel und Antetorsionswinkel
   Die beiden Winkel der Ausrichtung der Pfannenachse relativ zu den Körperebenen werden hier vom Operateur nach medizinischen Gesichtspunkten im Röntgenbild gewählt. Diese Winkel können ebenfalls vom Operateur intraoperativ verändert werden.
3. 3. Winkel in der sagittalen Körperebene zwischen vertikaler Achse und der Richtung vom Beckenkamm zur Symphyse.
   Durch die Bestimmung dieses Winkels wird eine intraoperative Bestimmung der Körperachsen und damit des Planungskoordinatensystems ermöglicht.

The surgeon has to determine the following values in the planning of a hip joint implantation for the acetabulum:

1. 1. Size of the artificial pan
2. 2. inclination angle and anti-torsion angle
   The two angles of the orientation of the pan axis relative to the body levels are selected here by the surgeon from a medical point of view in the X-ray image. These angles can also be changed intraoperatively by the surgeon.
3. 3. Angle in the sagittal plane of the body between the vertical axis and the direction from the iliac crest to the symphysis.
   By determining this angle, an intraoperative determination of the body axes and thus of the planning coordinate system is made possible.

It is assumed that the patient is supine at the beginning of the operation; The doctor has an X-ray available, which sufficiently reveals the overall anatomical constellation and the condition of the bone. He gains first ideas about the implant size to be used and the preferred coarse alignment of the implant. An incision is made 3 cm to 5 cm posterior to the Spina Iliaca Superior Anterior with a length of 4 cm, exposing the iliac crest and exposing the tissue to the rasp.

Fig. 1 shows a iliac crest locator 1 with associated mounting bracket 3, which is mounted in the exposed area of the iliac crest. The mounting bracket 3 comprises a medial clamp part 3.1 and a lateral clamp part 3.2, which are screwed together via an Allen screw 5 until the mounting bracket is firmly seated on the iliac crest. The actual iliac crest locator 1 has a crescent-shaped body 1.1 with a socket 1.2 for attachment to the mounting bracket 3 and a 4-point Lokatorfeld 1.3 of four IR-reflecting balls, each partially from a (not separately designated) spherical segmented diffuser Avoiding interference are surrounded. These are so-called passive targets or adapters, which are known as such and whose mode of operation in connection with a - also known - stereo camera arrangement of a so-called navigation system is therefore not further described here. After plugging the locator 1 is rotated relative to the mounting bracket 3 such that the Lokatorfeld is properly aligned with the camera, without one of the reflective balls is shielded by another. Then, by screwing the locator with the mounting bracket, a rigid connection is made between the two.

Instead of the iliac crest, the multipoint transmitter 1, referred to above as the iliac crest locator, can also be fastened to the pan roof of the pelvis. This has the advantage that the above-mentioned (additional) incision in the area of the iliac crest becomes superfluous, but the attachment of the multi-point transmitter - which is then referred to as "surgical field locator" - less stable with weakened bone structure.

Fig. 2 shows in addition to the skeletal fixed locator 1 described above, a hand switch 7 with a rod-shaped, tapering towards an end button part 9, of which a holder 9.1 projects vertically, an approximately Y-shaped button body 7.1 and a 4-point Lokatorfeld 7.2, similar to the construction of the iliac crest locator described above. Similarly, the locators of the arrangement components described below are constructed so that the corresponding designation of the parts and description thereof are omitted.

At the beginning of the navigation sequence, various points of the plane of the operating table on which the patient is lying are touched with the manual button 7 in order to enable a determination of the position of the table level in the room. Although this is not required for the actual determination of the patient's situation, it can be used for plausibility considerations (for example with regard to the significance of a pelvic inclination of the patient in relation to the level of the table, etc.). For the actual navigation, it is usually assumed that the patient frontal plane is parallel to the table level.

Subsequently, characteristic bony references in the pelvic region are palpated with the manual button 7 above the skin. First, the left and right iliac crest and the middle of the symphysis are touched. With these three touched points and the comb-symphysis angle determined in the planning, the body axes can be clearly defined. The direction from the center of the iliac crest to the symphysis is rotated about the transverse axis of the symphysis angle to represent the vertical body axis (orthogonal to the transverse axis). The sagittal body axis results from the first two axes as orthogonal.

Fig. 3 Figure 11 shows, in addition to the iliac crest locator 1, a femoral locator 11 with associated adapter (femoral clip) 13 for attachment near the proximal end of the femur. The femur clip 13 has a two-part main body of a bifurcated in plan view and in side view approximately L-shaped first base part 13.1, protrude from the two pins 13.2 for plugging the locator, and one with the first base part 13.1 latched, in the side view approximately L -shaped second base. The structure of the femur locator 11 itself corresponds - apart from an angled Lokatorstab - essentially that of the iliac crest locator.

It is plugged via a socket 15.1 at the free end of a locator rod 15 on one of the two pins 13.2 of the femoral clip 13.

Then the femoral clamp 13 is fastened with the attached locator rod 15 on the lateral femoral side approximately at the level of the trochanter minor or between the trochanter minor and the greater trochanter by pushing the muscle groups lying there aside and inserting the clamp. The rotation position should be selected so that the locator rod protrudes laterally out of the surgical field, preferably in the direction of the camera. Then the clip becomes medium torque tightened that actual Lokatorfeld (not separately designated here) plugged and aligned to the camera and finally screwed the femur Lokator.

Thereafter, the hip kinematic center of rotation in both the hip-fixed and femur-fixed coordinate systems is determined by several relative measurements of the femoral locator in the hip-fixed coordinate system at different leg positions. The transformation of all measured values can thus take place from the hip-fixed coordinate system into the coordinate system of the body axes. Allows all calibrated tools to be aligned to the body axis coordinate system; see below. With the center of rotation as the origin of the implant can be used at its kinematic origin. If corrections are required, shifts and angular changes in the planning can be performed intraoperatively.

After the operator has made the position detections in the various leg positions in "interactive" user guidance (again providing error correction due to plausibility calculations), the femur locator is removed from the bracket 13 and the femoral head is resected. The diameter of the resected head is measured and, based on the measurement result, a suitable hemisphere is selected for the next step, namely the determination of the center of the acetabulum or geometric center of rotation of the hip.

As Fig. 4 shows, the selected hemisphere 17 with a hand button 7 'of in Fig. 2 shown and described above to a ball adapter-hand button combination 19 together. By controlling this locator in the pan area (usually assuming a certain anteversion angle, eg 12 °) on the one hand, the validity of the determined by the femur locator (kinematic) rotation center from a geometrical point of view, and on the other hand allow the results of a "cross-check" to the implantation planning values from a geometrical point of view. In addition, by moving the hemisphere 17 in the pan area hints to win on possible mechanical collisions. The construction of the half-shell and its adaptation to the hand-held push-button always realizes the tip of the probe in the ball center of the antispherical ball.

Subsequently, in the context of the stored evaluation program with interactive user guidance, the final planning of the implantation takes place, from the determination of the implant size to be used up to displacement values and angle values. On this basis and on the basis of previously entered specific instrument data, the system calculates target positions for the resecting or setting instruments to be used or, more precisely, for their effective sections.

Fig. 5 shows in addition to iliac crest and femur locator 1, 11 a cutter-locator combination 21 with a milling shaft 23, a Fräswellenadapter 25 and a locator 27, the structure of which substantially to those of the femoral locator 11 after Fig. 3 equivalent. This instrument is aligned in the manner shown in the figure in a pan area, wherein the position and orientation detected due to the position signals from the Lokatorfeld and on screens in the in Fig. 6 shown way visually illustrated. A correct position of the milling cutter according to the planning data is indicated by a ring extending around the milling shaft in the display and by acoustic signals.

Once a pan fit is made in accordance with the design data, the cutter-locator combination is converted to a setting instrument-locator combination 29 as described in U.S. Pat Fig. 7 is shown. Here again, the locator 27 is used, now in conjunction with a setting instrument shaft 31 and a shaft adapter 33. With this instrument is in a largely analog for handling the cutter-locator combination and also shown on the PC screen a way Acetabulum 35 set. Their final position is entered into the system by the surgeon.

Subsequently, the shaft preparation and implantation (initially a test shaft), either in a conventional or also supported by the navigation system way done. Height and anteversion of the shaft are fixed according to the planning data; only the ball neck length is still freely selectable. Then, the joint is assembled with the test shaft and stability and any collisions when moving the shaft in the pan checked. In addition, a rough examination of the leg length is done by comparing the position of the ankle of the operated leg of the healthy. If joint stability problems occur, an attempt will be made to solve them by selecting a particular ball or stem of a different size from a ready-made assortment.

Optionally, in this phase measurements can also be taken on the other leg using the navigation system, the results of which, in the sense of symmetry considerations, can be used to fine-tune the implant. It is understood that such measurements employ a femoral locator modified for external application over the skin instead of the femoral locator described above.

An essential advantage of the proposed system is that, using navigation data, it is also possible to compare leg lengths (at the diseased hip before the operation and during the above-mentioned checking step in the final phase of the operation) before and after the leg length. For this, the femur locator is again positioned and fixed on the holder remaining on the femur and the position is detected with the leg extended and aligned parallel to the body longitudinal axis. The obtained position data provide evidence for any leg extension or leg shortening as well as for the so-called lateralization or medialization, ie the "lateral" position of the femur. If there is evidence of excessive medialization (inward displacement), a different stem may be used in conjunction with another ball, if appropriate, compared to the test stem; In any case, the measured values provide the physician with instructions that must be taken into account in the further care of the patient.

The following remarks refer to a use of the described system in stem preparation and implantation.

The placement of the stem of a hip prosthesis requires the production of a planned anti-torsion angle of the femoral neck and the angular production of the original leg length. The axis alignment of the shaft depends largely on the position of the medullary canal in the femur. This has the consequence that only from this the actual stem size or its offsets can be calculated.

With the help of a calibrated awl, the medullary canal of the femur is determined. Another important information for the placement of the stem is the determination of the center of rotation; see above.

Fig. 8 shows a usable for this purpose further component of the proposed arrangement, namely a Markkanalahlen-Lokator combination 37 with a Markkanalahle 39, A Ahlenadapter 41 and (again) a locator 27, similar to the already in Fig. 3 locator version shown. To insert this navigation instrument, the proximal end of the femur is opened with a box chisel or a jigsaw in the vicinity of the greater trochanter and the medullary canal 39 is inserted there from the proximal end.

Preoperatively, the angle of inclination and the angle of antetorsion of the femoral head are determined in the X-ray image and entered intraoperatively. In addition, the intraoperative determination of the antetorsion angle is possible by measuring landmarks on the knee joint and on the upper ankle joint, whereby intraoperatively the body levels are known. The actual implantation angles and positions of cup navigation can be taken into account during stem implantation. The last spatial position of the pan can be applied as a relative correction of the shaft. This procedure ensures optimal implantation.

The preparation of the femur for inserting the shaft is then - analogous to the preparation of the socket seat with a navigated cutter - with a navigated sheep rasp, ie a Schaftraspel-Lokator combination, which in Fig. 8 shown combination is very similar and therefore neither shown nor described in detail here. After preparation, a test shaft is again inserted and the checks described above in connection with the cup side navigation are carried out. With satisfactory results, the final shaft is then used, without this would have to be navigated again.

The embodiment of the invention is not limited to the above-described arrangement and the procedure outlined in connection herewith, but also possible in modifications which are within the scope of expert action.

LIST OF REFERENCE NUMBERS

1

Iliac crest locator

1.1

body

1.2

receptacle

1.3

4-point Lokatorfeld

3

Crab

3.1

Medial clamp part

3.2

Lateral clamp part

5

Allen screw

7; 7 '

hand switch

7.1

Button base body

7.2

4-point Lokatorfeld

9

button part

9.1

holder

11

Femoral locator

13

femoral

13.1

first basic part

13.2

spigot

13.3

second basic part

15

Lokatorstab

15.1

receptacle

17

hemisphere

19

Ball adapter manual switch combination

21

Router locator combination

23

auger

25

Fräswellenadapter

27

locator

29

Setting instrument locator combination

31

Setting instrument shaft

33

Socket adapter

35

acetabulum

37

Medullary canal Ahlen locator combination

39

Markkanalahle

41

Ahlen adapter

Claims (10)

1. Arrangement for the examination of function-determining geometric parameters of a joint in a vertebrate, in particular, a human hip or shoulder joint, in preparation for the insertion of a joint replacement implant, in particular, an acetabular or glenoid implant or an associated shaft implant, by means of an optical coordinate-measurement technique, comprising:

   - a stereo camera or camera arrangement for the spatial registration of optical sensor signals,

   - a mobile multi-point sensor (7; 37), which is designed as a mobile sensor for sensing bony references in the joint region in order to determine their coordinates;

   - a skeletally-fixed multi-point sensor (1, 3), which is designed for rigid attachment, in particular, by screwing or clamping, to an extremity extending from the joint, in particular, close to the proximal end of a femur or a humerus;

   - an interactive process-control unit for controlling the sequential registration and storage of a quantity of measuring-point coordinates delivered by the mobile multi-point sensor and of quantities of multi-point coordinates registered in a first plurality of positions of the skeletally-fixed multi-point sensor in a plurality of rotational positions of the extremity and their subsequent processing according to a previously-stored processing procedure;

   - an evaluation unit for evaluating the quantities of multi-point coordinates delivered by the multi-point sensors and registered by the camera arrangement for the purpose of determining the geometrical parameters, which comprises means for determining the transversal, vertical and sagittal body axes and means for the execution of an iterative process, in particular, an equalisation calculation according to the method of least squares, in order to determine the coordinates of the rotational centre of the joint; and

   - an output unit (Figure 6) connected to the process-control unit and the evaluation unit for the display of action requirements to an operator according to the predetermined processing procedure and dependent upon the results of the determination of the geometric parameters, and for the display of the evaluation results.
2. Arrangement according to claim 1,
   characterised by
   a further skeletally-fixed multi-point sensor (11, 13), which is designed for rigid attachment, in particular, by screwing or clamping, to a bony, cavitary region of the joint, in particular to an iliac crest or an acetabular roof, wherein the interactive process-control unit is also designed to control the registration and storage of a quantity of measuring-point coordinates delivered by the further skeletally-fixed multi-point sensor, and the evaluation unit is designed for the evaluation of the same.
3. Arrangement according to claim 1 or 2,
   characterised in that
   the output unit (Figure 6) is designed to display the evaluation results in a graphic display, in particular, in a synoptic-image display with a two-dimensional or three-dimensional image of the joint region obtained through an image-providing investigative technique.
4. Arrangement according to any one of the preceding claims,
   characterised by
   a first and second adjustable clamping device (3, 13) as an adapter for fixing the first and second skeletally-fixed multi-point sensor to the joint or respectively to the extremity.
5. Arrangement according to any one of the preceding claims,
   characterised in that

   - a third skeletally-fixed multi-point sensor is provided for substantially-rigid attachment, in particular, by means of an adjustable cuff, to a second extremity, which extends from a second hip or shoulder joint, which is not be operated; and

   - the evaluation unit is designed for the determination of geometrical parameters of the second hip or respectively shoulder joint as a reference for the geometric parameters of the first joint.
6. Arrangement according to any one of the preceding claims,
   characterised in that

   - the mobile, multi-point sensor (1, 3) is designed for the external sensing of bony references on the second extremity extending from the joint to be replaced and optionally from the second hip or shoulder joint, or that a further multi-point sensor designed as a mobile sensor for sensing references of this kind is provided for this purpose; and

   - the evaluation unit for evaluating the measuring-point coordinates of these bony references is designed for the determination of at least one of the geometric parameters, in particular, the length of the extremity.
7. Arrangement according to any one of the preceding claims,
   characterised by

   - a resection instrument (23), in particular, a milling or rasping device, which can be rigidly connected with the mobile multi-point sensor or with a further multi-point sensor to a geometrically-calibrated, navigable tool-sensor unit (21), in such a manner that position coordinates of an active portion of the resection instrument, in particular, of a milling head or a rasp portion can be determined from the sensor signals of this unit, and, optionally, position coordinates of a resection portion created with the resection instrument can be determined from the latter;

   - a formation of an input interface for the input of instrument parameters of the resection instrument.
8. Arrangement according to any one of the preceding claims,
   characterised by

   - a navigable setting instrument (31), which can be rigidly connected with the mobile multi-point sensor or further multi-point sensor to a geometrically-calibrated tool-sensor unit (29) in such a manner that position coordinates of an active portion of the setting instrument can be determined from the sensor signals of this unit;

   - a formation of an input interface for the input of tool parameters of the setting tool.
9. Arrangement according to any one of the preceding claims,
   characterised by

   - a probe, in particular, a medullary-canal awl (39) for probing a medullary canal of the extremity extending from the joint, which can be rigidly connected with the mobile multi-point sensor or a further multi-point sensor to a geometrically-calibrated, navigable probe-sensor unit (37) in such a manner that the position of the axis of the medullary canal can be determined from the sensor signals of this unit; and

   - a formation of an input interface for the input of probe parameters.
10. Arrangement according to any one of claims 1 to 9,
    characterised in that
    the process-control unit provides means for menu control including an input stage for the input via keyboard or phonetic input of defined, real or virtual points of the joint region, and/or of relative-position vectors between such points within the joint region, or from the latter to points relevant to joint function on the extremity outside the joint region, or for the data transfer of corresponding data of a three-dimensional image from an evaluation program of an image-providing investigation, and including a display stage for a planning result.

Images